Thursday, January 31, 2008

Solar Hot Water Heating






We spent some time analyzing the solar hot water heater installed on the Forfar motel. Prior to our arrival we had heard several reports regarding the system. It’s definitely not working, it’s definitely working, it might be working, it might not be working. The students and I discussed the system, during our class, reviewed the design, piping, flow rates, etc. We then decided on a set of changes we believed would improve the performance of the system. As a means of testing these changes we started by installing a Metrima BTU meter. This clever little device measures the temperature on the collector supply and return line, and the flow through the collector loop and reports the kilowatt hours of energy generated by the system. It is a utility grade meter. We then set about making our changes and monitoring the system. Our series of changes included 1) installing a shutoff valve in the electric tank which would require the system to draw off water from the solar tank rather than from the main water line when hot water was in use., 2) cleaning the solar thermal and PV panel driving the pump, 3) replacing the 5 watt PV panel with a 10 W panel, 4) replacing the 3.5 W circulating pump with a 10watt pump, 5) moving the thermal loop return to the electric water heater lower in the tank, and the elecric heating element higher in the tank. Through a systemeatic change and monitor approach we improved the system performance significantly over the week of our studies in solar thermal work. Pictures show the students installing the Metrima and making the first changes to the system. We improved the performance so much that we had to install an antiscald device in the system to ensure no one gets cooked in the shower.